Filtration systems for particulate matter reduction in outdoor air: a review

Outdoor particulate matter (PM) pollution poses a critical socio-economic and public health challenge worldwide. This review systematically evaluates over 250 studies on PM sources, health impacts, and outdoor filtration strategies, with a focus on both active and passive approaches. Our objectives were to (i) categorize major PM emission sources: transport, industry/construction, agriculture, and natural sources; (ii) assess the performance and operating costs also possibility of recycling, regeneration of leading active outdoor filtration systems (e.g., SMOG Free Tower, Mann + Hummel filter cube, electrostatic filters, etc.); (iii) examine passive methods such as urban green walls, passive outdoor filters, passive house air regulation. In the current trending, numerical modeling (CFD) emerges as indispensable for optimizing large-scale deployment, with the possibility of integration with artificial intelligent to predict the outcome results. We conclude that integrating targeted active units with passive methods offers a great cost-effective benefice for PM mitigation plan, potentially applicable in the same time for short- and long-term strategies in urban management.